Air convective warmer with noise reduction filter

ABSTRACT

To reduce the noise level of an air convective warmer, the air filter of the warmer is fitted with an air intercept mechanism to disrupt the flow of air that traverses inside the interior cavity of the air filter. By thus disrupting the air flow, the noise that otherwise would have been generated due to a non-interrupted air stream flow is lowered. The air intercept mechanism may be in the form of at least one partition positioned inside the interior cavity of the air filter. Alternatively, double-ended open tubes may be used, so long as the interior cavity of the filter is sealed, with only the tubes providing the passages for air to output from the air filter. Yet a third embodiment of the air reduction filter has an air impermeable material covering at least one portion of the surface area of the filtering material to prevent the inflow air from directly entering into the interior cavity of the air filter through the covered surface area.

FIELD OF THE INVENTION

The instant invention relates to air convection warmers and moreparticularly to an air convection warmer that operates at a lower noiselevel and yet produces the same throughput of temperature regulated airto inflate a convective blanket.

BACKGROUND OF THE INVENTION

To regulate the body temperature of a patient so as to preventhypothermia in the patient, a convective blanket that provides aconstant stream of warmed air to the patient is used. Convectiveblankets are inflated by air convective warmers. Most, if not all, airconvective warmers produce a high level of noise, at least for some ofthe patients and others who may be close to the machine. This is becauseblowers are utilized in the convective warmers to propel a stream ofair, heated or otherwise, from an air inlet to an air outlet, in orderto inflate the convective blanket. The noise from the blower, along withthe air stream flow through the convective warmer, tend to producesubstantial noise. Such substantial noise could be an annoyance to thepatient. The noise from the air convective warmer therefore needs to bereduced.

Prior to the instant invention, attempts have been made to reduce thenoise of air convective warmers. Such attempts include U.S. Pat. No.6,126,393 and its related U.S. Pat. No. 6,254,337. These patentsdisclose the configuration of an air blower unit in which the air inletis pointed toward the surface onto which the housing of the air blowerunit rests. The outlet for the air blower is provided at a side of thehousing, and is coupled to an air hose that has an elbow bent between45° and 90°. Thus configured, noise generated by the warmer allegedly isabsorbed by the elbow, and the noise waves that are not absorbed by theelbow are allegedly reflected downwardly onto the support surface by theelbow.

Another attempt to reduce the noise of an air blower is disclosed inU.S. Pat. No. 5,733,320. In the '320 device, noise cancellationcomponents are used. Such noise canceling components include an inputsensor such as a microphone, a sound source such as a loud speaker, anoise cancellation controller and an optional error microphone. An audionoise cancelling signal, 180° out of phase with the noise measured bythe input microphone, is output from the loudspeaker to cancel out thenoise.

Yet another attempt to reduce the noise level of an air convectivewarmer is disclosed in U.S. Pat. No. 7,037,068, assigned to the assigneeof the instant application. In the '068 device, indentations areprovided at the interior surface of the plenum chamber of the warmer tosuppress the noise. The disclosure of the '068 patent is incorporated byreference herein.

SUMMARY OF THE PRESENT INVENTION

The air convective warmer of the instant invention is an improvement ofthe existing EQUATOR® air warmer manufactured by the assignee of theinstant application. Instead of reconfiguring the construction of theair warmer, the inventors found that by disrupting the air flow patternin the air filter, the noise of the machine which presumably resultsfrom the blower and the air stream passing through the housing of thewarmer, could be substantially reduced. Thus, instead of having tomodify the whole machine, only the air filter of the air convectivewarmer needs to be reconfigured, thereby enabling the manufacturing ofan air warmer with a reduced noise level. So, too, the noise level ofair warmers that are already in service can be readily reduced by simplyretrofitting those warmers with the inventive air filter.

The inventive air filter has a base onto which an air filtering materialis mounted. The filtering material extend upwards circumferentially fromthe base to form a circumferential wall, the top of which is capped by acover that has an opening so that it looks as if there is a “donut hole”in the interior of the air filter, when the air filter is viewed fromthe top. It is through the top opening that air, sucked in through andfiltered by the circumferential filtering material wall of the filter inthe interior of the air filter, passes to the air blower of the warmer.

The filter is positioned adjacent to the air inlet of the convectivewarmer so that the incoming air is input to the machine through thefiltering material of the filter. The filtered air, upon passing throughthe filtering material, arrives at the interior of the air filter andfrom there passes through the top opening to the heating element, or theair conditioning unit, where the temperature of the incoming air iseffectively altered to colder or warmer air. From there, assuming thatthe air conditioning unit is a heater for the remainder of thedisclosure, by means of the blower, the heated air is output to the airoutlet of the warmer for inflating a convective blanket connected to thewarmer.

To disrupt the flow of air from the filter to the plenum of the warmer,a first embodiment of the instant invention provides for the placementof at least one partition inside the interior of the air filter so thatthe volume of space in the interior of the air filter is divided. Byempirical study, it was found that the optimal reduction of noise, fromapproximately 55.6 decibel to approximately 44.1 decibel for theEQUATOR® air warmer for example, is achieved when three partitions areplaced into the interior of the filter, with each partition extendingfrom the base of the filter to substantially the top opening of thefilter. It was found that the efficiency of the air flow output by theair blower is not decreased. The optimal number of partitions may ofcourse be dependent on the size of the machine, as well as the filteritself, and therefore may vary—be more or less than the mentioned threepartitions—dependent on the machine and the filter used for theparticular machine.

A second embodiment for interrupting the flow of air in the filter is bymeans of sealing the top opening of the filter, and extending throughthe sealed cover at least one open ended tube into the interior of thefilter. The end of the tube that is extended into the filter isspatially separated from the base of the filter so that air may passfrom the interior of the filter to the air plenum of the warmer throughthe open-ended tube. By providing a plurality of open-ended tubes, itwas found that the air flow in the interior of the filter is disruptedin such a way that the noise level generated by the warmer issubstantially reduced, and yet at the same time, the strength of the airstream flow from the warmer is not reduced, so that the efficiency withwhich the air warmer inflates the convective blanket connected theretois not affected.

The air flow from the filter may also be interrupted by the covering ofa portion of the filtering material by an air impermeable material, forexample, a piece of plastic, so that the air input to the interior ofthe air filter passes into the air filter from only one portion of thefiltering material. Further, for the air filter with the partition(s),the air flow is interrupted by having to go around the air filterbetween the partitions and the filter material and through the filtermaterial into the interior of the filter. The inventors found that to beoptimum, approximately ¼ to ¾, and preferably approximately 55%, of thefiltering material be covered by the air impermeable material to bothreduce the noise level and to continue to maintain the effectiveness ofthe air output from the air warmer.

The instant invention therefore relates to an apparatus for outputtingtemperature regulated air to an inflatable blanket at a reduced noiselevel that comprises a housing having an air inlet and an air outlet, anair conditioning unit, a blower for directing air from the air inlet tothe air conditioning unit and from there to the air outlet to inflatethe blanket, and an air filter interposed between the air inlet and theair outlet to filter the air from the air inlet, with the air filterhaving fitted thereto air intercept mechanism for interrupting the flowof air traversing through the air filter to the blower to thereby reducethe noise generated by the flow of forced air in the housing andattributable to at least the air blower.

The air intercept mechanism may be in the form of at least one partitionpositioned inside the interior of the air filter, with the partition(s)extending from the base to substantially the air output opening of theair filter. The air intercept mechanism may also comprise a cover thatseals the opening of the air filter to the plenum of the air warmer, andat least one open-ended tube that extends from the cover into theinterior of the air filter so that the air in the interior of the airfilter is output through the tube to the plenum of the air warmer. Theintercept mechanism may also comprise an air impermeable material shapedto cover a portion or portions of the circumferential surface of thefiltering material of the air filter so that air from the air inletpasses into the interior of the air filter only through the portion(s)of the filtering material that is not covered by the air impermeablematerial.

The instant invention is also related to an air warmer for outputtingtemperature regulated air to an inflatable convective blanket thatcomprises: a housing having an air inlet and an air outlet; an airconditioning unit; a blower for directing air from the air inlet to theair conditioning unit and from there to the air outlet to inflate theblanket; at least one temperature sensor for sensing the temperature ofair at the air outlet; an air filter interposed between the air inletand the air outlet to filter the air from the air inlet, with the airfilter having a base, an interior surrounded by a filtering material andan opening that allows air passing through the filtering material intothe interior of the air filter to be routed to the air conditioning unitand the blower; and an air intercept mechanism fitted to the air filterfor disrupting the flow of air traversing through the air filter to theblower.

The instant invention also relates to the method of reducing noise in anair convective warmer that has a housing having an air inlet and an airoutlet, a blower to direct the air input from the air inlet to the airoutlet, and an air conditioning unit to treat the air input from the airinlet so that temperature regulated air is output from the air outlet toinflate a convective blanket connected thereto. The method in particularrecites the step (a) of positioning an air filter in the housing betweenthe air inlet and the air outlet so that air from the air inlet passesthrough the air filter, and the step (b) of fitting to the air filter anair intercept mechanism for disrupting the flow of air in the air filterbeing routed to the air conditioning unit and the blower.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will become apparent and the invention itself willbe best understood with reference to the following description of theinvention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an exploded overall view of the air warmer of the instantinvention, with the various components of the air warmer shown;

FIG. 2 shows a prior art air filter;

FIG. 3 shows the air filter of the instant invention;

FIG. 4 shows a bottom view of the air warmer of the instant invention inwhich a portion of the base of the air filter of FIG. 3 has been removedto illustrate the placement of the partitions of the air filter of FIG.3 relative to the heater and the opening to the plenum of the airwarmer;

FIG. 5 a is an illustration of a second embodiment of the inventive airfilter of the instant invention;

FIG. 5 b is a semi cross-sectional exposed view of the FIG. 5 a filtershowing the positioning of the tubes in the interior space of the airfilter; and

FIG. 6 shows another embodiment of the air filter of the instantinvention in which a portion of the filtering material of the filter iscovered by an air impermeable material.

DETAILED DESCRIPTION OF THE INVENTION

With reference to exploded view of FIG. 1, the air convective warmer ofthe instant invention is shown to include a housing that is made up ofan upper part 2 a and a lower part 2 b. Lower housing 2 b has an opening4 onto which an air plenum 6 is fixedly positioned over, by means ofshown screws. Although air plenum 6 is shown to be in two parts, withair outlet 6 a being separate from the body proper of the air plenum, itshould be appreciated that air plenum 6 could in fact be made of aone-piece construction, with the air outlet 6 a being an integral partof the main body of the air plenum. Positioned between opening 4 and airplenum 6, at the latter's opening 6 c, is a heater 8, or an airconditioning unit, that is placed over opening 4 of housing 2 b. Agasket 10 is placed between heater 8 and plenum 6, when air plenum 6 isassembled to the interior of housing 2 b. Air outlet 6 a is fitted toopening 12 at the back of housing 2 b in such a way that the machine end14 a of an air hose 14 is connectable or matable to air outlet 6 a. Theblanket end 14 b of hose 14 is configured to be connectable to aconventional air convective blanket, not shown. Whether there is asecured connection between air outlet 6 a and hose inlet 14 a isdetermined by a micro switch sensor 16 mounted to the back of housing 2b.

An impeller, or blower fan 18 is positioned within the cavity of airplenum 6. Impeller 18, which is a part of the air blower of the airconvective warmer, is mounted to a motor mounting plate 20, which inturn has mounted on its upper side a motor 22 whose drive shaft isconnected to impeller 18 through an opening 20 a provided at plate 20.Motor 22 is controlled by the electronics on motor driver board 24,which is mounted to motor mounting plate 20. Additional electronics areprovided in a control panel (not shown as it is mounted within upperhousing 2 a), so that the speed with which impeller 18 is driven, aswell as power provided to heater 8 to vary the temperature that heatsthe air input to the air blower, at air plenum 6, may be controlled.Further, the control panel controls the readouts and other indicationsprovided at display 28 of housing 2 a. The power supplied to thedifferent components are provided by the power distribution board 26.The voltage used is controlled by mains filter 33. Various otherelectrical connections for the air warmer are also shown. They are notdiscussed herein insofar as the operation of a conventional airconvection warmer is well known and need not be further discussed. Thetemperature of the air at the outlet/hose end of air hose 14 may besensed by a sensor (not shown) provided at the outlet/hose end, whichoutputs a feedback signal to the control panel, so that feedback controlmay be provided to regulate the temperature of the air output from theair convective warmer to inflate or maintain the inflation of theconvention blanket. Pole support part 31 is provided to the back ofhousing 2 b to enable the air convective warmer to be mounted to a pole.

Prior to the instant invention, an air filter 32, such as that shown inFIG. 2, is mounted to the underside of housing 2 b, per shown at uppercorner view 34 of the figure, so that air is input to the air filter byway of slot or channel 36. Channel 36 may be referred to as the airinlet for the air warmer of FIG. 1. Air filter 32 has a base 38 ontowhich a filtering material 40 circumferentially extend upwards to form asubstantially donut shaped hole, otherwise referred to as the interior42 of the filter. A cover 43 caps the top of the filtering material 40to effect an opening 44 at the top of the filtering material. It isthrough opening 44 that the air in the interior 42 of filter 32 that haspassed through and been filtered by filtering material 40 is output tohousing 2 b, more specifically to the cavity of air plenum 6. Air filter32 is fitted to the base of housing 2 b, as shown by view 34.

With the air filter of FIG. 2, the air convection blower such as thatshown in FIG. 1 works efficiently. However, it also produces a noiselevel that may be deemed high by some patients and/or users. Onemeasurement of the noise generated by an air convective warmer fitterwith the air filter of FIG. 2 was 55.6 decibels. Most of the noisegenerated by the air blower is due to the movement of the air blower,more specifically the impeller 18, as it is being driven by motor 22,and the flow of the air stream from air inlet 36 through air filter 32,and from there through air outlet 6 a to air hose 14 to inflate and/ormaintain the inflation of the convective blanket (not shown) connectedto the air hose 14.

The inventors have discovered that by disrupting the air flow ininterior 42 of air filter 32, the noise level generated by the airconvective warmer may be substantially reduced. To achieve thisdisruption of air flow, a first embodiment of a modified air filter tobe used the in the air convective warmer of FIG. 1 is shown in FIG. 3.As shown, air filter 132, like the air filter of FIG. 2, has a base 138to which a filtering material 140 extends circumferentially to form anenclosed cavity 142 wherein ambient air passes from air inlet 136through filtering material 140. An opening 144 is provided at air filter132 for the filtered air in cavity 142 to be routed to housing 2 b, andmore specifically the cavity of air plenum 6, as indicated by itsopening 6 c. The filter material 140 is held in place by glue or otheradhesive to base 138, and a top rim or cover 143 is attached to orcovers the top of the filtering material to form the opening 144.

The inventors have found that by fitting the air filter with an air flowinterrupt mechanism, the nosie level of the air convective warmer may bereduced. For the embodiment of the air filter of FIG. 3, the air flowinterrupt mechanism of the air filter comprises at least one partition146 being positioned in the interior 142 of the air filter to disruptthe air flow routed from the environment to the air plenum of thehousing of the air convective warmer. Such disruption in fact causes thenoise level of the air convective warmer to be lowered. By empiricalstudy, it was found that for the size and dimension of the air filtershown in FIG. 3, which is to be used with the air convective warmer ofFIG. 1, an air disrupt mechanism that comprises three partitions 146a-146 c positioned within interior 142 of the air filter provide theoptimum result. This is not to say that a fewer or a higher number ofpartitions would not work just as well. A measurement taken with theplacement of three partitions in the interior of the air filter of FIG.3 shows that the noise level is reduced from the previously mentioned55.6 decibels to approximately 44.1 decibels during the operation of theair convective warmer fitted with the inventive filter. As shown in theupper corner diagram 134 of FIG. 3, air filter 132 is mounted to thebottom of housing 2 b by means of four screws 148.

FIG. 4 shows the bottom view of the air convective warmer, particularlyits housing portion 2 b to which base 138 of air filter 132 is coupledby means of screws 148. For demonstration purposes, a portion of base138 has been cut out to show the interior or cavity 142 of the airfilter 132, and the partitions 146 a to 146 c which divide the volume ofthe interior space 142 of the air filter into three substantially equalportions. Note that the air filter is positioned underneath opening 4,to which heater 8 superposes over. Thus, as air from the environment isinput to the air convective warmer through air inlet 136 due to thesuctioning effect of impeller 18, the sucked in air passes through thefiltering material 140 into interior cavity 142 of the air filter. Dueto partitions 146, the air flow within the interior cavity of the airfilter is disrupted. And it was found that such disrupted air flowactually reduces the noise of the flow of the air stream through airplenum 6, as well as the sound produced by the blower, as the intake airpasses heater 8 it is warmed, and then is routed to air outlet 12. Atthe same time, the amount of air as well as the efficiency with whichthe warmed air output by the air convective warmer of the instantinvention to inflate a convective blanket connected to the air warmerare determined not to be affected by the air filter fitted with the airinterrupt mechanism.

A second embodiment of the noise reduction air filter of the instantinvention is shown in FIGS. 5 a and 5 b. The same components for theFIG. 5 embodiment as those shown in the FIG. 3 embodiment are labeledthe same. As shown, the opening of air filter 132, which is formed byrim 143, is sealed by a cover 150. The interior cavity 142 of air filter132, as best shown in FIG. 5 b, is thereby enclosed, except for channelsthat are created by a plurality of open-ended tubes 152. Respectivefirst open ends of tubes 152 are attached to cover 150 to therebyprovide openings or apertures 152 a to the opening 4 of housing 2 b andalso therefore the internal cavity 6 c of air plenum 6. The otherrespective open ends of tubes 152, designated 152 b in FIG. 5 b, arespatially separated from base 138 by a predetermined distance 154, sothat the filtered air in cavity 142 of air filter 132 passes throughopen ends 152 b of the open-ended tubes 152 and from there passes intocavity 6 c of air plenum 6 by way of openings 152 a, after being warmedby heater 8. The inventors found that the air filter shown in theembodiment of FIG. 5 works equally well in reducing the noise of the airconvective warmer, as tubes 152 would disrupt the air flow from airfilter 132 to air plenum 6, and yet at the same time not affecting theamount of warmed air output from the air convective warmer to inflatethe convective blanket connected thereto. Note that even though sixtubes 152 are shown, a smaller or a greater number of tubes may be usedfor the FIG. 5 embodiment to reduce the noise level of the airconvective warmer of the instant invention.

Another embodiment of the noise reduction air filter of the instantinvention is shown in FIG. 6. For this embodiment, to disrupt the airflow inside the interior cavity 142 of air filter 132, an airimpermeable material 156, such as plastic, is wrapped about a portion ofthe circumferential surface of the filtering material 140. Althoughshown as wrapping around the outside circumferential surface offiltering material 140 in FIG. 6, it should be appreciated that the airimpermeable material 156 may in fact be placed against the insidecircumferential surface of filtering material 140 from within theinterior cavity of air filter 132. So long as the air impermeablematerial prevents the air from the environment from passing directly ororthogonally from all external directions through the filtering material140 into the interior cavity 142 of air filter 132, it was found thatthe air flow inside the air filter is disrupted. As shown in FIG. 6, byblocking at least one portion, or portions, of filtering material 140with the air impermeable material 156, the ambient air is prevented frompassing directly or orthogonally through the covered portion of theexternal surface of the filtering material 140 into air filter 132. Byempirical studies, the inventors found that an optimal reduction of thenoise level of the air convective warmer may be gained by coveringapproximately over one half of the surface area of the filteringmaterial 140 of the air filter, either circumferentially at the externalsurface as shown or internally at the internal surface of the filteringmaterial. The noise level of the air convective warmer nonetheless maybe reduced even were the surface area of the filtering material 140covered from approximately 40% to 60%, instead of the optimal overone-half surface area noted above.

In operation, once the air convective warmer is properly connected tothe air convective blanket by means of air hose 14, upon activation ofthe air convective warmer, due to the rotation of blower impeller 18,ambient air is sucked in from air inlet 136 and passes into the interiorcavity 142 of air filter 132 through the filtering material 140. Due tothe disruption of the air flow in the interior cavity 142 of the airfilter 132, the air that passes heater 8 and sucked into cavity 6 c ofair plenum 6 due to the rotation of impeller 18 does not generate asmuch noise as when there is no disruption to the airflow. The amount ofair output from the air convective warmer to the convective blanket,however, remains substantially unaffected by the interruption to the airflow so that the efficiency of the air convective warmer is notdecreased.

1-20. (canceled)
 21. In combination, a housing having an air inlet andan air outlet; a plenum positioned within the housing where air from theinlet flows; a fan to effect an airflow between the air inlet and theair outlet through the plenum; an air filter interposed between the airinlet and air outlet for filtering the air input to the plenum due tothe movement of the fan; and an air intercept mechanism within thehousing for disrupting the air flow of filtered air in the plenum toreduce the noise level generated by the movement of the fan and the flowof air between the air inlet and the air outlet.
 22. The combination ofclaim 21, wherein the air intercept mechanism comprises at least onepartition that disrupts the air flow from the air inlet to the plenum.23. The combination of claim 22, wherein the air filter has an interior,and wherein the at least one partition is positioned in the interior ofthe air filter.
 24. The combination of claim 21, wherein the airintercept mechanism comprises a plurality of partitions workingcooperatively with the air filter to disrupt the air flow into theplenum.
 25. The combination of claim 21, wherein the intercept mechanismoutputs at least one channeled air flow in the plenum.
 26. Thecombination of claim 21, wherein the intercept mechanism comprises anair impermeable material positioned to disrupt the air flow that passesthrough the air filter.
 27. The combination of claim 21, wherein the fanis positioned within the plenum and is adapted to route the air suckedin from the air inlet to the air outlet to inflate a convective blanketfluidly connected to the air outlet when in operation.
 28. Thecombination of claim 21, further comprising a heater positioned in thehousing relative to the plenum to heat the air input from the air inlet.29. An air warmer comprising: a housing having an air inlet and an airoutlet; a plenum inside the housing in fluid communication with the airinlet and the air outlet; a fan in the housing when in operation adaptedto drawn air from the environment into the plenum via the air inlet andoutput the air in the plenum as an air stream to the air outlet; an airfilter for filtering input air drawn into the plenum from theenvironment; and air intercept means positioned in the path of the inputair for disrupting the flow of the air stream traveling in the plenumfrom the air inlet to the air outlet to reduce the level of nosieresulting from at least the operation of the fan.
 30. The air warmer ofclaim 29, wherein the air intercept means comprises at least onepartition that disrupts the flow of air drawn in from the environmentthrough the air filter.
 31. The air warmer of claim 29, wherein the airfilter comprises an interior, and wherein the at least one partition ispositioned in the interior of the air filter.
 32. The air warmer ofclaim 29, wherein the air intercept means comprises a plurality ofpartitions working cooperatively with the air filter to disrupt the flowof the air stream in the plenum.
 33. The air warmer of claim 29, whereinthe air intercept means channels at least one air stream of filtered airinto the plenum from the filtered air drawn in from the environment. 34.The air warmer of claim 29, wherein the air intercept means comprises anair impermeable material positioned to disrupt the air flow passingthrough the air filter.
 35. The air warmer of claim 29, wherein the fanis positioned within the plenum to route the air drawn in from the airinlet as an air stream to the air outlet for output when the fan is inoperation.
 36. In an air warmer having a housing including an air inletand an air outlet, a plenum within the housing, a fan positioned in thehousing adapted to effect an air flow of the air drawn in from the airinlet to the air outlet, a method of reducing at least noise generatedby the fan when it is in operation, comprising the steps of: a)interposing an air filter in the housing between the air inlet and theair outlet to filter input air drawn through the air inlet from theenvironment; b) positioning air intercept means in the path of the inputair for disrupting the flow of the air stream in the plenum when the fanis in operation; whereby the level of nosie resulting from at least theoperation of the fan is reduced.
 37. The method of claim 36, wherein thestep (b) comprising the step of providing at least one partition todisrupt the air flow in the plenum.
 38. The method of claim 36, whereinthe step (b) comprises channeling at least one air flow from the airfilter to the plenum.
 39. The method of claim 36, further comprising thesteps of: positioning the fan within the plenum; operating the fan toroute the air drawn in from the air inlet to the air outlet as an airstream to inflate a convective blanket fluidly connected to the airoutlet.
 40. The method of claim 36, further comprising the step of:positioning a heater in the housing relative to the plenum to heat theair drawn in from the air inlet.